1. Field of the Invention
The present invention relates to systems for feeding and transporting documents and to a method and system for tracking document trailing edge position.
2. Background Art
A typical system for feeding and transporting documents includes a feeder and a separator in the document feeding portion of the system, and a series of roller pairs or belts in the document transporting portion of the system. In the feeding portion of the system, the feeder acts with the separator to feed documents singly, in order, from a stack. In the transporting portion of the system, the roller pairs and/or belts convey the documents, one at a time, past other processing devices such as readers, printers, and sorters that perform operations on the documents. The feeder is typically a feed wheel, but may take other forms. The separator may be a wheel, but also may take other forms such as a belt. Further, the components in the transporting portion of the system may take a variety of forms. Systems also include a component in the document feeding portion of the system that nudges documents into the nip between the feeder and the separator. A suitable nudger may be a nudger wheel, but may take other forms. An existing document feeder is shown in U.S. Pat. No. 6,199,854. That patent describes a document feeder with a variable speed separator.
In existing systems for feeding and transporting documents, operations that depend on the position of the document are generally performed in the transport stage, or transporting portion of the system For example, U.S. Pat. No. 5,848,784 describes a document separation apparatus. That patent describes the downstream acceleration/deceleration of documents with pinch rollers to adjust document spacing.
For the foregoing reasons, there is a need for a method and system for tracking document trailing edge position that allows operations that depend on the position of the document to be performed in the feeder stage, or feeding portion oft he system
It is, therefore, an object of the present invention to provide a method and system for tracking document trailing edge position that detects and tracks the trailing edge prior to the feeder.
In carrying out the above object, a method of tracking a document in a system for feeding and transporting documents is provided. The document has a leading edge and a trailing edge. The system includes a feeder stage and a transport stage downstream of the feeder stage. The feeder stage includes a feeder and a separator. The method comprises detecting the document trailing edge at a fixed location upstream of the feeder, and tracking a position of the document trailing edge as the document trailing edge moves between the fixed location and the feeder. The method further comprises performing an operation dependant on the document trailing edge position when the document trailing edge is between the fixed location and the feeder.
In a preferred embodiment, detecting further comprises providing a tachometer at the fixed location upstream of the feeder, and detecting a deceleration of the tachometer indicating when the document trailing edge passes the fixed location.
Tracking, in embodiments of the present invention, may take many forms. For example, the feeder may be a constant velocity feeder, and tracking would comprise starting a timer upon detection of the document trailing edge at the fixed location. For example, the feeder may include a tachometer that produces an output. Tracking would further comprise tracking the position of the document trailing edge based on the feeder tachometer output as the document trailing edge moves between the fixed location and the feeder. The feeder tachometer may include an encoder with the feeder tachometer output being a pulse sequence, or the feeder tachometer output may be an analog velocity signal.
Further, in carrying out the present invention, a system for feeding and transporting documents is provided. Each document has a leading edge and trailing edge. The system comprises a feeder stage including a feeder and a separator, a transport stage downstream of the feeder stage, and a tachometer at a fixed location upstream of the feeder. Control logic is configured to detect a deceleration of the tachometer indicating when the document trailing edge passes the fixed location The control logic is further configured to track a position of the document trailing edge as the document trailing edge moves between the fixed location and the feeder, and provides an output signal. The system further comprises a control device. The control device receives the output signal, and is configured to perform an operation dependent on the document trailing edge position when the document trailing edge is between the fixed location and the feeder.
Tracking, in embodiments of the present invention, may take many forms. For example, the feeder may be a constant velocity feeder with the control logic being further configured to start a timer upon detection of the document trailing edge at the fixed location. Further, for example, the feeder may include a tachometer that produces an output, and the control logic would be further configured to track the position of the document trailing edge based on the feeder tachometer output as the document trailing edge moves between the fixed location and the feeder. The feeder tachometer may include an encoder with the feeder tachometer output being a pulse sequence, or the feeder tachometer output may be an analog velocity signal.
The advantages associated with embodiments of the present invention are numerous. For example, embodiments of the present invention provide methods and systems for tracking document trailing edge position prior to the trailing edge reaching the feed wheel. Tracking the trailing edge position while the document is still in the feeder allows operations to be performed on the document, as well as other operations to be performed while the document is still in the feeder. In addition, knowing the trailing edge position allows a system to know when to perform operations on subsequent documents. Many document processing products could benefit from embodiments of the present invention. For example, copiers, fax machines, sheet feeders for computer printers, automatic teller machines, and document image scanners are just a few examples of products that could benefit from embodiments of the present invention.
The above object and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the preferred embodiment when taken in connection with the accompanying drawings